1. Field of the Invention
The present invention relates to a display device and drive method thereof and relates in particular to a display device and drive method capable of displaying different aspect ratios.
2. Description of Related Art
In recent years, so-called wide vision (high vision) having an aspect ratio of 16:9 has been developed, as compared to the standard aspect ratio of 4:3 for television (NTSC method, etc.). Video camera equipment is also being developed having a high filming mode for wide vision. The development of wide vision has increased the demand for display devices having a screen aspect ratio of 4:3 for standard television systems to also have wide vision display capability with an aspect ratio of 16:9.
Wide vision requires a display with a large screen. Panel displays such as electroluminescence display devices (EL) and liquid crystal displays (LCD) not requiring much space are ideal for use as large screen displays. A feature of these liquid crystal display devices is that theoretically little drive power is required thus allowing utilization such as in electrical view finders (EVF) in video camera equipment.
However, the aspect ratio must be switched according to the television system being used so that the display device is compatible with television systems having different aspect ratios. Therefore, in the liquid crystal display device disclosed for instance in Japanese Patent Laid-open No. 5-199482, in the effective display area with pixels arrayed in lines, the voltage potential of the scanning electrode for a specified number of pixels at the top and bottom edges of that display area was made to equal the voltage potential of the signal electrode. In the liquid crystal display device disclosed for instance in Japanese Patent Laid-open No. 8-314421, processing was performed to write black color information in a specified number of scanning lines at the top and bottom edges of the effective display area.
However, in either of these examples of the related art, circuits such as memories or scan converters were required in the drive system to drive the display for displaying different aspect ratios, causing the problem of the additional costs required for those circuits. A liquid crystal display device such as utilized in EVF of video camera equipment, having a simple design and low power consumption, was therefore demanded, capable of displaying different aspect ratios, and with as low a cost and simple a structure as possible.
In view of the above mentioned problems with the conventional art, this invention has the object of providing a display device and drive method thereof, with a simple design, low cost, low power consumption, and capable of displaying different aspect ratios.
The display device of this invention is comprised of a pixel section containing pixels arrayed in lines, a vertical drive system to sequentially set each pixel of that pixel section to active status a line at a time, a control circuit to set the pixels of a specified area on the upper and lower or right and left of the pixel section to active status when a control signal is applied, and a horizontal drive system to write a specified luminance level signal for all pixels of an area set in active status by this control circuit, and also write for pixels of all other areas, display signals in each line sequentially set to active status by the horizontal drive circuit.
In the display device of this configuration, the control circuit sets each pixel of a specified area of the upper and lower (or left and right) of the pixel section to active status regardless of vertical scanning by the vertical drive system, when a control signal is applied for switching the aspect ratio for instance from 4:3 display screen to a 16:9 display screen. The horizontal drive system supplies a specified luminance level signal to the pixel section at this time. A specified luminance level signal is thus written in all pixels of a specified area of the upper and lower (or left/right of pixel section) of the pixel section. In areas other than the specified area however, along with making each pixel active a line at a time sequentially by vertical scanning in the vertical scanning system, a display signal is written in each line by horizontal scanning of the horizontal drive system.